The formation and evolution of dwarf galaxies in diverse cosmological environments

波长冷暗物质(Lambda冷暗物质)宇宙学模型是目前解释宇宙大尺度结构的首选范例。然而，要使其小规模的预测与矮小星系的观测结果保持一致，就会带来巨大的挑战(例如，Bullock和Boylan-Kolchin，2017)。根据恒星质量低于~10^9 Msol和暗物质晕质量低于~10^11 Msol进行分类，矮小星系代表了宇宙中一些最古老和最暗的物质主导系统，它们浅的引力势井使它们对各种内部和外部天体物理过程特别敏感。因此，它们是测试星系形成模型和主流宇宙预测的灵敏探测器。最近，深度光学调查促进了更多、越来越暗的矮星系的发现，预计即将到来的维拉·鲁宾天文台将极大地加快新发现的速度。现有的观测已经揭示了最暗矮星的基本性质之间的显著差异，包括它们的运动学、大小、气体含量和恒星形成历史。到目前为止，在数值模型中再现这些性质被证明是具有挑战性的。此外，最微弱的矮星的形成机制仍然不确定，这是当代天体物理学前沿的一个重大问题。目前的主要假设是，它们是早期宇宙的遗迹，在高红移时形成，并在再电离时代(Simon，2019)熄灭。这篇博士论文旨在通过运行下一代最先进的星系形成模型：COLIBRE的宇宙学放大模拟来仔细检验这一假设。COLIBRE包含了比目前最先进的星际气体物理更复杂的处理方法，以及通过使用等质量重子和暗物质粒子实现的卓越动力学。因此，它非常适合于研究矮小星系。我们将通过创建一系列模拟来研究不同环境中的矮小星系，这些模拟是对旗舰COLIBRE运行的补充：这些将是从(300Mpc)^3 Eagle-XL母体体积中选择的“变焦”球状区域。每个星体的半径为5-10Mpc(由计算限制决定)，具有不同的平均过密度，但没有大质量的光晕(M200和GT；10^12Msol)。后一种情况减少了计算成本，并允许我们在模拟大体积的同时将分辨率提高到每个重子粒子10^4Msol。

The lambda Cold Dark Matter (lambda CDM) cosmological model is the currently-preferred paradigm for explaining the large-scale structure of the cosmos. However, reconciling its small-scale predictions with observations of dwarf galaxies poses outstanding challenges (e.g. Bullock and Boylan-Kolchin, 2017). Classified by stellar masses below ~10^9Msol and dark matter halo masses below ~10^11 Msol, dwarf galaxies represent some of the oldest and most dark matter dominated systems in the cosmos, and their shallow gravitational potential wells make them particularly sensitive to a diverse range of internal and external astrophysical processes. They are therefore sensitive probes for testing the predictions of galaxy formation models *and* the prevailing cosmogony.Deep optical surveys have recently fostered the discovery of many more, ever-fainter, dwarf galaxies, and it is expected that the forthcoming Vera Rubin Observatory will dramatically accelerate the rate of new discoveries. Existing observations have already revealed remarkable diversity among the fundamental properties of the faintest dwarfs, including their kinematics, size, gas content and star formation histories. To date, reproducing these properties in numerical models has proven challenging. Moreover, the very formation mechanism of the faintest dwarfs remains uncertain, and poses a major question at the forefront of contemporary astrophysics. The leading hypothesis is, at present, that they are relics of the early universe, which formed at high redshift and were quenched during the epoch of reionization (Simon, 2019).This PhD thesis aims to scrutinise this hypothesis using cosmological zoom-in simulations run with the next-generation, state-of-the-art galaxy formation model: COLIBRE. COLIBRE ncorporates a more sophisticated treatment of interstellar gas physics than the current state-ofthe-art, in addition to superior dynamics achieved by using equal mass baryon and dark matter particles. It is therefore ideally suited to examination of dwarf galaxies. We will study dwarf galaxies in a diverse range of environments by creating a series of simulations complementary to the flagship COLIBRE run: these will be "zoomed" spherical regions, selected from the (300Mpc)^3 EAGLE-XL parent volume. Each will have a radius of 5-10Mpc (dictated by computational limitations), and with various mean overdensities but devoid of massive haloes (M200 > 10^12 Msol). The latter condition mitigates computational cost and allows us to increase the resolution to 10^4Msol per baryonic particle whilst still simulating a large volume.